This application claims the priority of German application 198 39 522.1, filed in Germany on Aug. 29, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a jerk pump provided for an internal combustion engine, with an integral solenoid valve in which a pump plunger driven by a cam delivers fuel at high pressure through a channel that extends in the pump housing and through an injection line to an injection nozzle, and in which an armature of the solenoid valve cooperates with a spring-loaded valve piston by which the high-pressure side guiding the channel can be connected with a low-pressure side.
Jerk pumps of this kind are known from MTZ Motortechnische Zeitschrift 57 (1996) 4, FIGS. 2 and 3, from Neue Motoren "Thermodynamik OM 904 LA, FIGS. 2 and 3, and from German Patent Document No. DE 196 41 952 A1 in which the valve piston permanently connected with the armature supports a spring plate that abuts a pressure shoulder of the valve piston by spring force. The valve piston is pressed against a valve stop by the spring force. As soon as the solenoid valve is activated, the valve piston strikes its valve seat against the spring force and interrupts the free connection between the high-pressure side and the low-pressure side. Injection begins and is terminated again only when the solenoid valve is deactivated and the pressure on the high-pressure side collapses.
In designs of this kind, because of the high switching rate, rebounding of the valve piston or re-opening of the valve cannot be avoided.
Hence, a goal of the invention is to provide simple means on the solenoid valve according to the species that minimize the rebounding of the valve piston or even prevent it entirely.
This goal is achieved by preferred embodiments of the invention by providing a jerk pump for an internal combustion engine, comprising: an integral solenoid valve in which a pump plunger driven by a cam delivers fuel under high pressure through a channel that extends in a pump housing and through an injection line to an injection nozzle, an armature of the solenoid valve cooperating with a spring-loaded valve piston by which a channel-guiding high-pressure side can be connected with a low-pressure side, wherein the valve piston has an absorbent body held in a resting position by spring force, said body striking a stop body that is in an operating connection with valve piston when the valve piston is on its valve seat.
Further advantageous features of preferred embodiments of the present invention are described below and in the claims.
As a result of the special arrangement of an absorbent body, it is possible to suppress and/or eliminate the undesired re-opening of the valve and/or the multiple rebounding of the valve piston.
In the resting state, the absorbent body is located at its stop or in its initial position. After the solenoid coil is energized, the valve piston is moved in the closing direction together with the absorbent body. As soon as the valve piston strikes its valve seat, the absorbent weight moves further in the closing direction under the influence of inertia. At the moment when the valve piston wants to rebound from its valve seat, the absorbent weight reaches its sleeve-shaped stop body. An opposite momentum is then generated that counteracts the rebounding of the valve piston.
When the valve opens, the absorbent weight can follow the valve piston only after a delay because of its mass inertia. As a result, an opposite momentum is generated that counteracts the rebounding of the valve piston from the stop.
In German Patent Document DE 197 08 104 A1, published subsequently, and in German Patent Document DE 40 20 951 A1, absorbent bodies for solenoid valves are mentioned, but an impact of the absorbent body against a stop body in an operating connection with the valve piston is not provided for closing movements.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.